1. Field of the Invention
The invention is directed to compositions and methods for recovering oil from waste oil fluids; and more particularly, the invention is directed to a method of recovering oil from waste oil fluids using water-soluble polymers dispersed in a concentrated salt media.
2. Description of the Prior Art
The recovery and recycling of oil from waste oil is becoming more important due to economics and stricter environmental EPA regulations regarding the disposal of waste oil. Generally, waste oils include dispersed solids and emulsified water. The solids and water should be removed if the oil is to be recycled. Untreated waste oils are considered hazardous and usually cannot be landfilled. Stricter regulations are driving customers to recycle more and to invest in the treatment of waste oils.
Table 1 classifies waste oils in the following industrial categories:
TABLE 1 ______________________________________ Classification of Oily Wastes % OIL % WATER % SOLIDS ______________________________________ Refining - Crude 90-95 5-10 0-5 Machining - Cutting 50-80 20-50 0-20 Waste Oil Sludges 40-50 40-50 5-10 Steel - Rolling Oils 80-95 5-20 0-5 ______________________________________
The Nalco Water Handbook, 1st Ed., 1979, page 11.
Refinery waste oil comes from two different sources: (1) Skimmings from the water clarification equipment, i.e., DAFs, APIs, and consisting mainly of crude oil; and, (2) Leakage from processes collected via traps and drains throughout the plant. This oil is usually sent to a wastewater treatment plant (WWPT).
One type of waste oil is formed during the process of removing dispersed oil from wastewater in wastewater treatment plants. The oil (called "float" or "skimmings") is concentrated in clarification vessels such as dissolved air floatation units (DAFs), induced gas floatation units (IGFs), corrugated plate interceptors (CPIs), and holding tanks. The oil floats to the top of these units, is removed by mechanical means and then stored. This waste oil may then be disposed of by incineration, sent to oil reclamation sites, or treated on-site. These waste oils have a minimum of 50% to 95% oil and contain emulsified water and solids which are stabilized by chemicals used to remove the oil from the waste water.
Several other examples of waste oil include waste oil from: oil production, oil refineries, aluminum and steel mills, laundries, automotive and chemical processing industries. One large source of waste oil is used motor oils.
One of the most effective methods of removing the solids and water in waste oil fluids is through the use of the chemical demulsifying aids. Typically, this application requires 10 to 100 times the dosage needed for other emulsion breaking applications, such as removing water from crude oil.
Historically, dry polymers, solution polymers, inverse emulsion latexes and metal ions have been used to assist in the treatment of waste oil. Each material has its own advantages and disadvantages. While dry polymers have the benefit of being extremely concentrated, thereby reducing shipping costs, the equipment to dissolve the polymers is expensive and is not available to all end-users on site.
Latex polymers also suffer from problems but are used quite frequently. Latex polymer preparations include 30-35% solids dispersed in oil. The latex polymer must be also inverted prior to use. Numerous problems associated with this feeding method have caused many customers to avoid latex polymers. In addition, the latexes generally have a very narrow treating range, often resulting in over-treatment at higher dosages.
Although solution polymers require no prior make up, the percent solids and molecular weight are severely limited due to the nature of the material. These materials are often used to break water-in-oil emulsions, but they are unable to precipitate the dispersed water and solids, thus requiring another chemical to accomplish this.
The water-soluble dispersion polymers of the invention offer many solutions to these problems and represent a new method for recycling and recovering industrial waste oils.